Terminal apparatus

ABSTRACT

A printing terminal apparatus for data transmission is adapted to transmit at the beginning of each message sent to a central computer, a code combination indicative of the terminal operator and to print characters corresponding to said code combination in a predetermined position on the paper at the printing terminal. The code combination is automatically generated at the start of the message by inserting a lock-key into a corresponding lock and by depressing a key associated with the inserted lock-key.

United States Patent 1151 3,678,179

Serracchioli et a]. [451 July 18, 1972 TERMINAL APPARATUS 2,574,362 11/1951 Warburton ..178/17A 3,281,803 10/1966 10611156111116: ..17s/17.5

[72] Inventors: Francesco Serraechioll; fiancesco Restivo,

both of Tonno Italy Primary Examiner-William C. Cooper [73] Assignee: Ing- C. Olivetti 8: Co., S.p.A., (Torino), Assistant Examiner-William A. Helvestine Italy Attorney-Birch, Swindler, McKie & Beckett [22] Filed: June 2, 1970 [21] Appl. No.1 42,716 57] ABSTRACT A printing terminal apparatus for data transmission is adapted [30] Foreign Application Priority Dim to transmit at the beginning of each message sent to a central June 3, 1969 Italy ..52094 A169 computeh a code combination indicative of the terminal operator and to print characters corresponding to said code 52 us. 01. ..17s/4.1, 178/17 A combination in a predetermined position on the p p at the [51] Int. Cl. ..1-104l15/34, 1-104121/00, H041 15/12 pri ing e min l. Th cod combination is automatically [58] Field of Search ..l78/4.l, 17 A, 17 C, 17.5 generated at the start of the message by inserting a lock-key into a corresponding lock and by depressing a key associated [5 6] References Cited with the inserted lock-key.

UNITED STATES PATENTS 1 1 Claim, 2 Drawing Figures 3,268,649 8/1966 Locke ..i78/4.l

njifps MODEM 14 Patented July l8, 1972 3,678,179

' v -2 Sheets-Sheet 1 MEMORY INVENTORS FRANCESCO ssannccmou FRANCESCO RESTIVO Patented Jul 18,1972 3,678,179

I 2 Sheets-Sheet? INVENTORS FRANCESCO SERRACCHIOLI :2: mm 6528 W25 J a o o 9G: QEEE FRANCES CO RESTIVO TERMINAL APPARATUS The present invention relates to a data terminal apparatus comprising a store, printing -and tabulation means, and adapted to be connected to a remote central processor.

In a complex data terminal/central processor system for processing in real time, for example, current accounts and savings deposits, security and the consequent control of the transactions operated peripherally constitutes a serious problem. In fact, a requirement felt on the part of banking institutions is that for peripheral control the operation accomplished on an individual terminal should be printed with an indication of the operator who has completed the given work, this indication being contemporaneously signalled to the central processor.

In some known apparatuses of a first type, reliance is placed upon the various operators who can operate on one and the same temrinal apparatus each of them keying their own identifying code. This does not give the required degree of security. In other known apparatuses of a second type, mechanical interlocks are present which exclude totally the operation of the apparatus. The blocking of the machine at a mechanical level, while resolving the problem of security, contrasts with the requirement of general efiiciency and of flexibility of the system, without resolving the problem of controlling all the transactions.

The object of the present invention is to overcome these disadvantages.

In accordance with the invention there is provided data terminal apparatus adapted to be linked to a remote processor and comprising a keyboard, a store, a control unit, a printing device, a tabulation device and means for enabling the operation of the apparatus, these means being adapted to generate a signal enabling the control unit to order the writing in the store and the printing at the terminal by the printing device of a code indicating the operator enabling the terminal apparatus.

The invention will be described in more detail, by way of example, with reference to the accompanying drawings, in which:

FIG. 1 is a block diagram of a terminal apparatus embodying the invention; and

FIG. 2 represents a more detailed diagram of the apparatus.

With reference to FIG. 1, the terminal apparatus is constituted by a keyboard 1 comprising a numerical portion, an alphanumerical portion, and a portion having function and control keys for forming and controlling the structure of the messages sent to the central processor. The codes introduced by the keyboard 1, through a channel 2, are sent to a control unit 3 of the terminal. The control unit 3 of the terminal is entrusted with the management of the entire apparatus, supervising all the logical functions of the same. The control unit 3 interacts with a store 4 which, in one particular embodiment, is of the dynamic type constituted by a magnetostrictive delay line having a capacity of 500 alphanumeric characters, each of 7+1 bits. The main functions of the store 4 are those of storing and preserving the interrogation messages introduced into the terminal and the reply messages coming from the central processor. The control unit 3 controls moreover a channel 5 for the introduction of data and commands to a printing device 6. The transmission and the receipt of messages on the part of the terminal along the transmission line 7 are controlled by a line control 8, which controls the conversation procedure between the terminal and the central processor.

The message coming from the store 4 through a channel 9 under the control of the control unit 3 is sent on a channel 10 to the line control 8. The line control 8 sends the message on a channel 11 to a serializer-parallelizer 12, which provides for serializing the bits of the message. The bits arranged in series are sent on an interface channel 13 to a modem 14 which provides for the modulation of a carrier wave for the transmission on the line 7.

When, on the other hand, the central processor wishes to send a message to the terminal, the line control 8 establishes the conditions for reception, whereby, when the terminal is ready to receive the bits of information received on the line 7 and demodulated by the modem 14, they are sent on the channel 15 to the parallelizer 12. The parallelizer 12 recomposes the individual characters and, through a channel 16, sends them to the line control 8 where a parity check may be effected; then the characters are sent on the channel 17 to the control unit 3, which controls them and sends them finally on the channel 18 to the store 4. The control unit 3 moreover orders the printing of the information by the printing unit 6 when a function character commands printing.

The line control 8 supervises the conversation procedure between processor and terminal, which can be either a polling procedure for sending inquiry messages from the terminal to the processor or a selection procedure for the transmission of answering messages from the processor to the terminal. The two procedures can be of the type described in US. patent application Ser. No. 818.916 filed on Apr. 24, 1969 in the name of Francesco Serracchioli.

The store 4 is constituted by a magnetostrictive delay line having the capacity of 500 characters. Each store cycle comprises 500 digit periods, each digit period comprising ten bit periods from D1 to D10. Each character in the store is represented by seven bits stored respectively in the seven binary positions corresponding to the bit periods from D3 to D9. The binary position corresponding to the bit period D10 is capable of containing a parity bit for the character. The position corresponding to the bit period D1 is capable of containing a service bit bs=l which, in the operation of writing in the store, is gradually shifted from one digit period (store cell) to the next, to indicate continuously the store cell into which the following character is going to be introduced. Similarly, the binary position corresponding to the second bit period D2 is capable of containing a service bit bhl which, in the operation of reading from the store, is gradually shifted from one digit period to the next to indicate the store cell from which the following character to be extracted from the store itself is going to be read.

At the head of the 500 X 10 binary positions of the store there is present a binary position capable of containing a timing startup bit CS and a binary position containing the relative parity bit PCS.

The serializer-parallelizer 12 and the modulator-demodulator 14 are of any conventionally known type; and do not need to be described in detail and are also of known type, commercially available, while the line control 8 can be of the type described in US. patent application Ser. No. 764.708 filed on Oct. 3, 1968, now US. Patent No. 3,5645] 1.

With reference to FIG. 2, the keyboard 1 is divided into four sections: Alphanumeric keyboard 19; numerical keyboard 20; function keyboard 21; and a control section.

The alphanumeric keyboard 19 comprising 42 alphanumeric keys and the reduced numerical keyboard 20 comprising 12 numerical keys are generally known in the field and do not need further explanation. The codes entered on these keyboards, respectively through a channel 22 and a channel 23, brought together in a channel 24, are sent to a logical control block 25.

A channel" is a communication route between logical blocks comprising several signals in parallel and is indicated in FIGS. 1 and 2 by a double line. It is the duty of the logical block 25 to receive the data arriving from the keyboards and to route it to the store 4 and to the printing unit 6. In fact, as codes are keyed in sequentially by the operator, the data is introduced through a channel 26 to a block 27 capable of introducing the bits constituting the characters into the delay line 28. The block 27 can be of the type described in the specification of US. patent application Ser. No. 868.132 filed on Nov. 21, 1969 in the name of Antonio Bartocci.

contemporaneously, the control block 25 sends the characters received from the keyboard through a channel 29 to the printing unit 6. The printing unit 6 is composed of three main parts: a functions recognition unit 30, a printing unit proper 31, and a tabulation device 32. The printing unit 6 communicates moreover respectively with the control unit 25 and a tabulation decoder 33, which will be further explained, through the timing lines 34 and 35. The functions recognition unit 30 recognizes the function characters received on the channel 29 and accordingly controls the specific functions of the characters themselves. In particular it is adapted to control the functions of tabulation, line feed, space, carriage return, and color selecting for the ink ribbon in a known manner. The characters not recognized by the unit 30 as expressing a particular function are transferred to the printing unit 31 proper, through the channel 36 in order to be printed. The printing unit 31 can be ofthe type described in US. Pat. No. 3.356.198 assigned to the same assignee as this invention. A timing signal is exchanged between the functions recognition unit 30 and the printing unit 31 proper on the line 37. The functions recognition unit 30, moreover, communicates through a channel 38, with the tabulation device 32. The tabulation device 32 can be of the type described in US. patent application Ser. No. 803.754 filed on March 3, 1969 in the names of Ricciardi and Sandrone, now abandoned. In particular the tabulation device 32 is constituted by a drum on the periphery of which there are arranged 120 metallic stops. Each stop is shaped so as to be able to command the stoppage of the printing unit on three tabulation programs, on two or on one alone; in particular the profile of the stops has a succession of teeth and of gaps suitably arranged on three different tracks and according to the stoppage positions desired for each tabulation program. In this way, the tabulation device 32 commands through the channel 39 the printing unit 31.

The function keyboard 21 comprises three tabulation bars. The three bars generate three respective codes TABl, TAB2, TAB3, which, sent on the channel 40 to the logical unit 25, are routed to the store 4 and to the functions recognition unit 30. The unit 30 recognizes the tabulation character received and gives a feed command to the printing device 31 on the channel 37, while through the channel 38 it acts on the tabulation drum 32 to select one of the three tabulation tracks present. When a tooth corresponding to the tabulation program selected is encountered, there is commanded through the channel 39 the stoppage of the printing device 31 at a longitudinal position corresponding to the position at which the tooth is stopped.

On the surface of the tabulation drum 32, the tabulation stops, besides the three tracks reserved for the tabulation and for the consequent control of the printing device 31, comprise three more tracks capable, according to a suitable arrangement of teeth and gaps, of actuating or not, respectively in correspondence with a tooth or a gap, three switches 41, 42, 43, The three electrical signals generated by the three switches 41, 42, 43 are decoded by the decoder 33. The decoder 33 can generate respectively on lines 44, 45, 46 commands for blocking the alphanumerical keyboard 19, the numerical keyboard and the function keyboard 21 in dependence upon the binary code combination received from the three switches 41, 42, 43. The blocking commands can be generated also by the control unit through lines 69, 70 and 71. The decoder moreover, in dependence on the combination received from the three switches 41, 42, 43 commands, through a channel 47, a code generator 48. The code generator 48 communicates the generated codes, through a channel 49, to the control block 25, which utilizes them as required. In particular, the decoder 33 orders the generator 48 to generate the end-of-message character ETX which, received by the control unit 25, is written in the store 4 to conclude the message contained in the store itself. Furthermore the decoder 33 commands the generator 48 to generate a particular service code which, received by the control unit 25, is sent to the functions recognition unit which brings about a particular function of the printing device 31, such as for example the opening of the conventional transparent bar of a front feeding device unit 31. This opening is effected each time a new accounting document is to be inserted in the machine, or each time a transaction has been completed.

The control unit 25 interacts furthermore, through the channels 50 and 51, with a block 52 which staticizes the states which the terminal apparatus can assume. In fact, the terminal apparatus possesses various states, the sequence of which depends on the conversation procedure with the central processor and on the internal operative functioning. The states of the terminal, in particular, are: free, assigned to keyboard, ready to transmit, transmission, assigned to computer, printing. The control unit 25 furthermore receives the characters stored in the store 4, through the channel 53, to which they are supplied from a circuit 54, capable of reading the bits written in the delay line 28. The circuit 54 can be of the type described in the aforesaid patent application Ser. No. 868.132. Finally the control unit 25 communicates, as has already been said, on the channels 10 and 17 with the line control unit 8.

As has been previously said, the keyboard 1 also comprises a control section. The control section is constituted by three lock switches indicated by S, A and B and by three corresponding keys S, A and B (i.e. keys which are depressed). The group of the three lock switches and of the three associated keys is capable of qualifying each type of transaction effected under local control and of obstructing any operation which the operator is not authorized to perform.

The keys S, A, B generate, by means of three associated microswitches, respectively three signals on lines 55, 56 and 57 which are sent to a combinatory network 58. The combinatory network 58 receives furthermore six lines 59-64 coming from the three lock switches S, A and B. Each lock can be turned into two positions by two different keys, whereby there can be sent six different commands to the combinatory network 58. The combinatory network 58 corrununicates with the control unit 25 through a channel 65.

The two diiferent positions of the keys in the locks S, A and B allow, only after consent of the corresponding keys S, A, B, the combinatory network to supply a qualifying and specific command to the control unit 25. In fact, with the key turned to the right in the lock A, the key A enables the combinatory network 58 to supply to the control unit 25 a command such that the unit 25 in its turn orders, through a channel 66, the code generator 48 to generate a code corresponding to the operator A. On the other hand, with the key turned to the left in the lock A, the key A enables the combinatory network 58, the unit 25 and the code generator 48 to generate a code corresponding to the operator C. With the key turned to the right in the lock B, the key B enables the combinatory network 58, the unit 25 and the code generator 48 to generate a code corresponding to the operator B. With the key turned to the left in the lock B, the key B enables the generation of a code corresponding to the operator D. With the key turned to the right in the lock S, the key S enables the generation of a code which designates the operator as the supervisor, while with the key turned to the left the key 8 enables the generation of a code which qualifies the operator as the maintenance engineer.

In the initial state, the terminal is in the free state which can be attained from a preceding operation of transmission or reception or else automatic reset in response to switching on the machine.

Let us suppose that one of the six possible different operators provided with his key wishes to initiate an operation. In particular, the operator A introduces his key into the lock A, turning it to the right, and then presses the corresponding key A. The combinatory network 58 receives the two commands on the wires 62 and 56 respectively, whereby, through the channel 65, it sends a command to the control unit 25. If in the printing unit 31 the carriage is at the beginning of a line, a rnicroswitch 66 is closed and sends a conditioning signal on the wire 67 to the control unit 25. The control unit 25, having received the conditioning signal on the wire 67 and the command qualifying the operator A on the channel 65, begins to accomplish the operations described below. In the first place, through the channel 50, it puts the state of the terminal into assigned to keyboard, then through the channel 26 it clears the magnetostrictive line 28 and orders, through the channel 66, the code generator 48 to emit the tabulation code TABl. The tabulation code TABl is sent through the channel 49 to the control unit 25, which sends it on the channel 29 to the functions recognition unit 30. The unit 30 starts the movement of the carriage of the unit 31 and contemporaneously selects the track 1 in the tabulation drum of the device 32, whereby the printing unit is stopped in the position corresponding to the first stoppage corresponding to the track selected with the code TABl. The three other tracks at the stoppage corresponding to the selected tabulation actuate in a suitable manner the three switches 41, 42 and 43, whereby the decoder 33 acts, through the wires 44, 45, 46, to unblock one or more of the keyboards 19, and 21 according to the combination of the signals emitted from the switches. The decoder 33 contemporaneously advises the control unit 25 through the line 68. The control unit 25 orders, through the channel 66, the code generator 48 to generate the code corresponding to the operator A. This code is routed by the unit 25 both into the first position of the store 28 and to the functions recognition group 30, which provides an order to the printing device 31 to print the code. In this way, the code of the operator is printed locally at the beginning of the operation and contemporaneously the code is recorded in the store at the beginning of the message which will be sent to the central processor. If the carriage of the printing unit 31 is not at the beginning of the line, the switch 66 is not actuated, whereby the control unit 25, not being enabled by the signal on the line 67, for placing the terminal apparatus at the disposal of the operator A, commands the code generator 48 to emit a line feed code NL. This code is sent on by the control unit 25 to the functions recognition unit 30 which orders the printing device 31 to line feed with return to the beginning of a line. At this instant, the carriage finds itself at the beginning of a line whereby the enablement signal is emitted along the wire 67, whereby the operator A, upon a fresh depression of the key A, starts the operations described above.

What we claim is:

1. A terminal apparatus for data transmission operable by various tenninal operators, having an input device for entering a message to be transmitted to a central processor, and a control unit for controlling said message transmission, wherein the improvement comprises:

a code generator operable for selectively generating code combinations,

normally ineffective locking means variably conditionable for causing operation of said code generator,

a plurality of locking-keys selectively assignable to each one of said terminal operators for rendering effective said locking means, each of said locking-keys conditioning said locking means according to a configuration identify ing the relevant one of said terminal operators, and

means comprised in said control unit for causing said locking means to operate said code generator for generating a code combination corresponding to said identifying configuration, said control unit causing the code combination so generated to be transmitted to said central processor together with the entered message.

2. Apparatus as claimed in claim 1, further comprising a memory connected to and conditionable by said control unit for temporarily storing said code combination generated by said code generator together with the entered message before said code combination and said message are transmitted to said central processor.

3. Apparatus as claimed in claim 1, comprising blocking means for blocking the operation of said input device, means controlled by predetermined machine conditions for rendering said blocking means effective, and releasing means included in said control unit and conditioned by said locking means for rendering said blocking means ineffective.

4. Apparatus as claimed in claim 1, wherein said locking means comprises a plurality of locks, each of said locking keys being associated with one of said locks and positioning said associated lock to identify the relevant operator.

5. Apparatus as claimed in claim 4, including a plurality of operator identifying keys each of said identifying keys being associated with said one of said locks and individually depressible for rendering effective the associated lock according to the identifying position of said lock.

6. Apparatus as claimed in claim 5 further comprising a combinatory network jointly conditioned by said locks and the depressed one of said plurality of identifying keys for generating signals identifying said relevant operator, said network being connected to said causing means to generate the identifying code combination for said relevant operator.

7. Apparatus as claimed in claim 5, wherein said input device comprises a keyboard, and comprising blocking means for blocking the operation of at least one portion of said keyboard, decoder means for decoding predetermined conditions in said apparatus for rendering said blocking means effective, and release means included in said control unit and jointly conditioned by said locks and said identifying keys for rendering said blocking means ineffective.

8. A terminal apparatus for data transmission operable by various terminal operators having an input device for entering a message to be transmitted to a central processor, an output device for presentation of said message, and a control unit for controlling said message transmission and said output device, wherein the improvement comprises:

manually operable locking means operated by corresponding lock-keys, each one of said lock-keys being assigned to one of said various terminal operators,

manually depressible keys, each of said keys being assigned to at least one of said various terminal operators, and

a code generator jointly conditioned by said locking means and said depressible keys for generating an operator identifying code and for causing said control unit to transmit the identifying code so generated together with said message to said central processor, and to activate said output device for presentation of said identifying code together with said message.

9. Terminal apparatus as claimed in claim 8, wherein said output device comprises a serial printer adapted to sequentially print characters, a paper support, a carriage transversely movable for changing the relative position of said support and said printer, and a tabulation device adapted to be activated for moving said carriage sequentially to a set of predetemiined columnar positions, characterized in that said control unit comprises activating means conditionable by said identifying code to activate said tabulation device, and means responsive to at least one position reached by said carriage to activate said printer for printing said identifying code.

10. Apparatus as claimed in claim 9, comprising a carriage position detector switch for generating a new line signal when said carriage is brought to a new line, said activating means being jointly conditioned by said identifying code and by said line signal for causing the movement of the carriage from the new line position to a predetermined line position.

11. A printing terminal apparatus for data transmission for operation by various terminal operators, having a keyboard for posting a message to be transmitted, a memory for temporarily storing the posted message, blocking means conditionable for blocking the operation of at least one portion of said keyboard, a serial printer adapted to sequentially print the characters so stored, a paper support for said printer, a carriage transversely movable for changing the relative position of said support and said printer, a tabulating device adapted to be activated for moving said carriage sequentially to a set of predetermined columnar positions, and a control unit for controlling the operation of said printer and said tabulating device and for transmitting the message so stored to a central processor, wherein the improvement comprises:

control means coupled to said blocking means and controlled by said tabulating device upon bringing said carriage to a predetemiined columnar position for so conditioning said blocking means,

a code generator operable for selectively generating code combinations,

a plurality of normally ineffective locks, each of said locks adapted to be variably positioned,

a number of locking-keys each of said keys assignable to one of said operators, at least two locking-keys cooperating with one of said locks for positioning said one lock to corresponding positions,

a plurality of operator identifying keys associated with said locks and individually depressible,

a combinatory network jointly conditioned by said depressed identifying key and the associated lock of said plurality of locks according to the key-directed position of said corresponding lock, for generating signals identifying said operator,

means comprised in said control unit and conditioned by said combinatory network for causing operation of said code generator to generate a code combination corresponding to said identifying signals, and

activating means comprised in said control unit and effective in response to said generation of said code combination for rendering said blocking means ineffective, said central unit controlling said memory to store said code combination together with the then entered message, and controlling said printer to print the character corresponding to said code combination together with said message in a specific one of said columnar positions of said carnage. 

1. A terminal apparatus for data transmission operable by various terminal operators, having an input device for entering a message to be transmitted to a central processor, and a control unit for controlling said message transmission, wherein the improvement comprises: a code generator operable for selectively generating code combinations, normally ineffective locking means variably conditionable for causing operation of said code generator, a plurality of locking-keys selectively assignable to each one of said terminal operators for rendering effective said locking means, each of said locking-keys conditioning said locking means according to a configuration identifying the relevant one of said terminal operators, and means comprised in said control unit for causing said locking means to operate said code generator for generating a code combination corresponding to said identifying configuration, said control unit causing the code combination so generated to be transmitted to said central processor together with the entered message.
 2. Apparatus as claimed in claim 1, further comprising a memory connected to and conditionable by said control unit for temporarily storing said code combination generated by said code generator together with the entered message before said code combination and said message are transmitted to said central processor.
 3. Apparatus as claimed in claim 1, comprising blocking means for blocking the operation of said input device, means controlled by predetermined machine conditions for rendering said blocking means effective, and releasing means included in said control unit and conditioned by said locking means for rendering said blocking means ineffective.
 4. Apparatus as claimed in claim 1, wherein said locking means comprises a plurality of locks, each of said locking keys being associated with one of said locks and positioning said associated lock to identify the relevant operator.
 5. Apparatus as claimed in claim 4, including a plurality of operator identifying keys each of said identifying keys being associated with said one of said locks and individually depressible for rendering effective the associated lock according to the identifying position of said lock.
 6. Apparatus as claimed in claim 5 further comprising a combinatory network jointly conditioned by said locks and the depressed one of said plurality of identifying keys for generating signals identifying said relevant operator, said network being connected to said causing means to generate the identifying code combination for said relevant operator.
 7. Apparatus as claimed in claim 5, wherein said input device comprises a keyboard, and comprising blocking means for blocking the operation of at least one portion of said keyboard, decoder means for decoding predetermined conditions in said apparatus for rendering said blocking means effective, and release means included in said control unit and jointly conditioned by said locks and said identifying keys for rendering said blocking means ineffective.
 8. A terminal apparatus for data transmission operable by various terminal operators having an input device for entering a message to be transmitted to a central processor, an output device for presentation of said message, and a control unit for controlling said message transmission and said output device, wherein the improvement comprises: manually operable locking means operated by corresponding lock-keys, each one of said lock-keys being assigned to one of said various terminal operators, manually depressible keys, each of said keys being assigned to at least one of said various terminal operators, and a code generator jointly conditioned by said locking means and said depressible keys for generating an operator identifying code and for causing said control unit to transmit the identifying code so generated together with said message to said central processor, and to activate said output device for presentation of said identifying code together with said message.
 9. Terminal apparatus as claimed in claim 8, wherein said output device comprises a serial printer adapted to sequentially print characters, a paper support, a carriage transversely movable for changing the relative position of said support and said printer, and a tabulation device adapted to be activated for moving said carriage sequentially to a set of predetermined columnar positions, characterized in that said control unit comprises activating means conditionable by said identifying code to activate said tabulation device, and means responsive to at least one position reached by said carriage to activate said printer for printing said identifying code.
 10. Apparatus as claimed in claim 9, comprising a carriage position detector switch for generating a new line signal when said carriage is brought to a new line, said activating means being jointly conditioned by said identifying code and by said line signal for causing the movement of the carriage from the new line position to a predetermined line position.
 11. A printing terminal apparatus for data transmission for operation by various terminal operators, having a keyboard for posting a message to be transmitted, a memory for temporarily storing the posted message, blocking means conditionable for blocking the operation of at least one portion of said keyboard, a serial printer adapted to sequentially print the characters so stored, a paper support for said printer, a carriage transversely movable for changing the relative position of said support and said printer, a tabulating device adapted to be activated for moving said carriage sequentially to a set of predetermined columnar positions, and a control unit for controlling the operation of said printer and said tabulating device and for transmitting the message so stored to a central processor, wherein the improvement comprises: control means coupled to said blocking means and controlled by said tabulating device upon bringing said carriage to a predetermined columnar position for so conditioning said blocking means, a code generator operable for selectively generating code combinations, a plurality of normally ineffective locks, each of said locks adapted to be variably positioned, a number of locking-keys each of said keys assignable to one of said operators, at least two locking-keys cooperating with one of said locks for positioning said one lock to corresponding positions, a plurality of operator identifying keys associated with said locks and individually depressible, a combinatory network jointly conditioned by said depressed identifying key and the associated lock of said plurality of locks according to the key-directed position of said corresponding lock, for generating signals identifying said operator, means comprised in said control unit and conditioned by said combinatory network for causing operation of said code generator to generate a code combination corresponding to said identifying signals, and activating means comprised in said control unit and effective in response to said generation of said code combination for rendering said blocking means ineffective, said central unit controlling said memory to store said code combination together with the then entered message, and controlling said printer to print the character corresponding to said code combinatioN together with said message in a specific one of said columnar positions of said carriage. 